As the city increases in population, its retail and business district necessarily expands also, the rise in values of the real estate forcing the wholesale interests farther away from the center. Traffic on these circuit arteries would thus change in character, and they might eventually be made boulevards to carry traffic of every description except that of heavy teaming. The argument for the circuit as described is equally strong when considered with regard to any form of traffic. It is based on a general experience in other cities, which proves that there is a gradual evolution from mere utility to a service of a lighter and more agreeable character. For example, the Square of the Innocents in Paris, once a cloistered cemetery, is now a playground, and serves as a breathing space for the densely populated neighborhood. Some such evolution will come in the case of the present freight yards lying along the river, which ultimately will be abandoned for freight purposes, just as the fortifications of Paris and Vienna have been transformed from absolute utility to useful purposes of an entirely different nature. When the freight yards shall be abandoned as industrial sites a large tract of territory will be available for public purposes, and the growing population might easily demand the space for recreation; and the fact that the available space lies along the river will be of double advantage, since river banks furnish an agreeable variety when they extend throughout a city. [Illustration: CIV. CHICAGO. VIEW OF DREXEL BOULEVARD.] In addition to the diagonals shown on the diagram are the existing roads running beside the great railway rights-of-way. Some of these already extend far out in the country, and also penetrate inside the city. All of them should be improved, and missing links should be supplied. When, at perhaps no distant day, the railroads entering the city come to be operated by electricity, no better highways can be imagined. They should be broadened, ornamented, and made to serve as great arteries. Outside the city limits, and often inside them, these highways beside the railways penetrate populous districts, where they are of increasing importance. They should be drained, paved, and planted in the best manner, and it is of first importance that there should be no grade crossings of carriageways and railways. This work of improvement which is already in progress inside the city should be carried on until every crossing within the territory shown on the main diagram or encircling highways shall be eliminated. [Illustration: CV. CHICAGO. VIEW OF MICHIGAN AVENUE, LOOKING NORTH.]